Additive manufacturing (AM), which is also called solid freeform fabrication (SFF) and three-dimensional (3D) printing, is a set of layer-by-layer processes for producing 3D objects directly from a digital model. The technology of additive manufacturing began a few decades ago. 3D printing technology is used for prototyping and for distributed manufacturing with applications in, for example, architecture, construction (AEC), industrial design, automotive, aerospace, military, engineering, civil engineering, dental and medical industries, biotech (human tissue replacement), fashion, footwear, jewelry, eyewear, education, geographic information systems, food, and many other fields. Currently, the additive manufacturing (3D printing) industry has grown to almost $3 billion in 2012 and is projected to grow to more than $6.5 billion by 2019. Wohlers Associates, “Wohlers Report 2012: Additive Manufacturing and 3d Printing, State of the Industry.” 2012, 1-271 (Ft. Collins, Co.) http://wohlersassociates.com/state-of-the-industry-reports.html.
The origin and evolution of additive manufacturing and the National Science Foundation's role in such origin and evolution are set forth in C. L. Weber, et al., “The Role of the National Science Foundation in the Origin and Evolution of Additive Manufacturing in the United States,” IDA Science & Technology Policy Institute, IDA Paper P-5091, 2013, which is attached hereto as Appendix A.
In general terms, additive manufacturing is a process that takes virtual blueprints from computer aided design (CAD) or animation modeling software and slices them into digital cross-sections for the machine to successively use as a guideline for printing. Depending on the machine used, material or a binding material is deposited until material/binder layering is complete and the final 3D model has been printed. When printing, the 3D printing machine reads the design and lays down successive layers of liquid, powder, paper or sheet material to build the model from a series of cross-sections. These layers are joined or automatically fused to create the final shape. The fundamental advantage of additive manufacturing techniques is their ability to create almost any shape or geometric feature.
In 3D printing machines that use an extrusion deposition process (also known as Fused Filament Fabrication (FFF)), a plastic filament (typically wound on a coil and unreeled to supply material) is used and is applied through an extrusion nozzle, which regulates the flow of the molten plastic bead by controlling the filament feed rate. The extrusion nozzle heats to melt the material (or otherwise renders the material flowable). The extrusion nozzle can be moved in both horizontal and vertical directions by a computer-controlled mechanism. Alternatively, the printer platform bed may be moved relative to the extrusion nozzle, or coordinated movements of both the nozzle and platform may be used to achieve the desired extrusion path in the x, y, and z directions. The model or part is produced by extruding small beads of thermoplastic material to form consecutive layers in the vertical (i.e., z) direction. The material hardens immediately after extrusion from the extrusion nozzle. Various polymers are used in such an extrusion deposition process, including, but not limited to, the following: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), high density polyethylene (HDPE), PC/ABS, and polyphenylsulfone (PPSU). Generally, the polymer is in the form of a filament, fabricated from virgin resins.
Currently, there is a disparity between traditionally manufactured polymer parts utilizing injection molding, extrusion molding, machining etc., and parts printed with additive manufacturing techniques such as Fused Deposition Modeling (FDM™) (Stratasys Inc., Minneapolis, Minn.) and Fused Filament Fabrication (FFF). Such disparity includes, for example, that the strength of the final part may be compromised when compared to parts produced through conventional machining methods. Accordingly, additive manufacturing capabilities are hindered by the weak weld between printed filaments, which often leads to delamination and mechanical failure. Thus, there is a need for a method to make an object using 3D printing that has the same or better mechanical properties as compared to those of conventionally manufactured objects (such as those objects made by injection molding, extrusion molding, machining, etc.).